When Fatigue Was Vasculitis: A Case of Limited PR3 ANCA-Positive Granulomatosis With Polyangiitis

Granulomatosis with polyangiitis (GPA) is a rare multisystem necrotizing vasculitis involving small to medium-sized vessels and is commonly associated with proteinase 3 antineutrophil cytoplasmic antibodies (PR3 ANCA). While pulmonary and renal manifestations are classically recognized, atypical presentations with predominant constitutional, sinonasal, ophthalmological, and endocrine manifestations may result in substantial diagnostic delay. We present the case of a 28-year-old woman with a two-year history of profound fatigue, generalized myalgia, anosmia, chronic sinonasal symptoms, headaches, painful eye movements, and secondary amenorrhea. Her symptoms progressed to significant impairment in activities of daily living because of severe fatigue and lower limb pain. The patient underwent extensive hematological and endocrine investigations, including lymph node biopsy and pituitary hormonal assessment, before the eventual diagnosis of PR3 ANCA-positive GPA. Computed tomography imaging demonstrated complete opacification of the right maxillary sinus with additional ethmoidal mucosal thickening, while autoimmune serology demonstrated strongly positive anti-PR3 antibodies with negative anti-myeloperoxidase (MPO) antibodies. The patient subsequently demonstrated marked symptomatic improvement following the initiation of oral prednisolone therapy. This case highlights the diagnostic challenges associated with ear, nose, and throat (ENT) predominant GPA in the absence of overt renal disease and emphasizes the importance of considering ANCA-associated vasculitis in patients with chronic inflammatory symptoms and refractory sinonasal disease.